The present invention relates to an orthopedic prosthesis. More specifically, the invention concerns prosthesis for restoring the functionality of an extremity, such as an arm of a patient. The invention is particularly suited for the replacement of all or any part of a right or left long bone of the patient.
The later half of the 20th century has seen a proliferation in the number of human skeletal components that can be replaced by a man-made prosthesis. Over the years these prosthesis have evolved from simply a physical substitution for a bone or a joint, to the more sophisticated fully functional prosthesis. For example, prostheses are well known for the replacement of the shoulder joint or the elbow joint. A modular shoulder prosthesis designed according to U.S. Pat. No. 5,314,479, assigned to DePuy, Inc., can be integrated into the existing glenoid cavity of a patient's shoulder. The prosthesis includes a lower stem that is configured to be embedded within the existing humerus bone of the patient. In a like manner, U.S. Pat. No. 6,290,725 (also owned by Depuy, Inc.) discloses a modular elbow prosthesis that includes stems for implantation into the intramedullary canal of the humerus and ulna bones. Similar prosthetic joints exist for replacement of the hip, knee, and ankle joints.
While many devices exists for the replacement of a damaged or defective joint, the substitution of a bone, and particularly a long bone, is much more problematic. While prosthetic phalanges have enjoyed increasing success, the long bones have not been so easily replaced by prosthesis, particularly to maintain the functionality of the patient's limb.
The problems with long bone replacement are many and varied. Perhaps the greatest difficulty is the extreme load-bearing nature of the long bones. A further problem associated with a long bone prosthesis is the variability in length of a particular long bone between patients. The femur, tibia, ulna, and humerus bones vary in length as much as patients vary in height. Many approaches have been implemented for adjusting the length of prosthetic joints. It should be noted that with these prosthetic joints, the joint is affixed to an existing long bone, such as by implantation of a stem into the intramedullary canal of the bone.
Yet an additional problem with total long bone prosthesis is that it is difficult to provide a prosthesis of the appropriate length prior to surgery because it is difficult to obtain an accurate pre-surgical measurement of the long bone. Inaccurate measurement of the long bone prosthesis of course leads to an improper length of the extremity. This mal-adjusted length can cause motor and muscular difficulties. Moreover, an incorrect prosthesis length can affect the tightness of the tissue surrounding the prosthesis. If the length is too short, the surrounding tissue is unnecessarily loose. If the prosthesis is too long, the tissue may be too tight, if the prosthesis can be implanted at all. Thus when a surgeon is to replace a long bone or a part of it with a prosthesis, it is desirable to have a prosthesis available of the anticipated length based upon pre-surgical measurement which can be easily lengthened or shortened.
Maintaining sufficient prosthetic devices to address the needs of total, proximal, distal and intercalary replacement of both the right and left long bones of patients can require a large inventory of prosthetics either at the hospital or a nearby medical supply company.
While the prior prosthetic devices have gone a long way toward helping patients with bone or joint disorders, several needs remain unmet. One need is for a viable long bone prosthesis or substitute that is suitable for replacement of the right or left long bone of a patient. Another need is for an adjustable length prosthesis that allows for easy and ready adjustments by substitution of parts during the surgery to implant the prosthesis within the patient. Another need is for a prosthetic system using common components to fabricate total, proximal, distal, and intercalary long bone prosthesis for both the right and left long bone.
In order to address these needs, the present invention contemplates a modular long bone prosthesis that can be readily configured using the same components as a right or left long bone total replacement. By substitution of standard components the length of the prosthesis can be varied.
According to one aspect of the disclosure, a modular long bone prosthesis is provided having a proximal component and a retroversion component. The proximal component is configured at a proximal end to receive a head forming a portion of a joint and is formed at a distal end to mate with additional prosthesis components. The proximal component is formed to simulate an angle inherent in the proximal end of the bone to be replaced and includes an indicator adjacent the distal end to facilitate rotational alignment of the proximal component and additional prosthesis components. The retroversion component includes a proximal end configured to mate with the distal end of the proximal component. The proximal end includes alignment indicia for positioning relative to the indicator on the proximal component. When the indicator is in a first position relative to the alignment indicia the proximal component and the retroversion component establish a first alignment orientation forming an angle simulating the angle inherent in the proximal end of the right long bone of the long bone to be replaced. When the indicator is in a second position relative to the alignment indicia the proximal component and the retroversion component establish a second alignment orientation forming an angle simulating the angle inherent in the proximal end of the left long bone of the long bone to be replaced.
According to a second aspect of the disclosure, a modular long bone prosthesis system is provided for replacing all or a portion of a long bone having a head and neck at its proximal end and a pivot axis about which the bone with which the long bone articulates pivots at the distal end. The system comprises a proximal component configured to replace the neck of the long bone and to receive a component for replacing the head at a proximal end, a distal component configured at its distal end to include a pivot axis about which the bone with which the long bone articulates may pivot, a retroversion component, a spacer component, and a stem component. The proximal component is configured to mount to either the retroversion component, the stem component or the spacer component on its distal end. The distal component is configured on its proximal end to mount to either the retroversion component, the stem component or the spacer component. The retroversion component is configured to mount at one end to either the distal component or the spacer component and at the other end to either the proximal component or the spacer component. The spacer component is configured at one end to mount to either the distal component or the proximal component and at the other end to either the retroversion component or the stem component. The stem component is configured at one end to mount to either the distal component, the proximal component or the spacer component and at the other end to be received in the intramedullary canal of the long bone. When coupled, the proximal component, distal component and retroversion component form a total long bone prosthesis exhibiting a retroversion angle found in the long bone. When coupled, the proximal and stem components form a proximal prosthesis. When coupled, the distal and stem components form a distal prosthesis.
According to yet another aspect of the disclosure, a modular humeral prosthesis system is provided for replacing all or part of either a right or left human humerus having a head forming a retroversion angle with the pivot axis of the forearm. The system comprises a proximal component configured to replace the neck of the humerus and to receive a component for replacing the head of the humerus at a proximal end, a distal component configured at its distal end to include a pivot axis about which the forearm pivots, a retroversion component, a plurality of spacer components, and a stem component. The proximal component is configured on its distal end to mount to either the retroversion component, the stem component or one of the plurality of the spacer components. The distal component is configured on its proximal end to mount to either the retroversion component, the stem component or one of the plurality of the spacer component. The retroversion component is configured to mount at one end to either the distal component or one of the plurality of the spacer components and at the other end to either the proximal component or the one of the plurality of spacer components. Each spacer component is configured at one end to mount to either the distal component or the proximal component and at the other end to either the retroversion component or the stem component. One of the plurality of spacer components is longer than the other of the plurality of spacer components. The stem component is configured at one end to couple to either the distal component, the proximal component or the spacer component and configured at the other end to be received in the intramedullary canal of the long bone. The proximal component, distal component and retroversion component when coupled form a total humeral prosthesis exhibiting a retroversion angle found in the humerus. The proximal and stem components when coupled form a proximal humeral prosthesis. The distal and stem components when coupled form a distal humeral prosthesis.
Additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.